A reception/small party, (often involving cake or some form of refreshments), held when a person hated by everyone in the workplace is either resigning, or being "let go." Everyone's more than happy to "give them cake, and show them the door."

Shane (upon seeing the refreshments laid out): Ooh, is it someone's birthday?
Clive: No, haven't you heard? Mary just got a higher-paying position with another firm!
Shane: Awesome! Time to give that bitch a cake-and-door party!